MIM, or metal injection molding, is an industrial technique for preparing metal powders or using metal powders (or mixtures of metal powders and non-metal powders) as raw materials, going through forming and sintering to obtain metal materials, composite materials, and various types of articles.
At present, MIM has been widely used in transportation, machinery, electronics, aerospace, weapons, biology, new energy, information and nuclear industries, and has become one of the most dynamic branches of new materials science.
In this post, we will introduce you the material properties and the detailed manufacturing process of MIM, so that you can manufacture your products more effectively. Let’s get started!
When you use technology in the production process, you first need to understand the characteristics and professional features of the technology. Therefore, the first part of this post is something about material properties.
1. What are the material properties for MIM?
MIM has a unique chemical composition and physical properties that are not available in conventional fusion casting methods. The use of MIM technology can directly produce porous, semi-dense or fully dense materials and products, such as oil-impregnated bearings, gears, cams, guides, tools, etc, without cutting process.
1) MIM technology can minimize the segregation of alloy components and eliminate coarse or uneven cast structure, which plays an important role in the production of high-performance rare earth permanent magnet materials, rare earth hydrogen storage materials, rare earth luminescent materials, rare earth catalysts, and high-temperature superconducting materials.
2) A series of high-performance and non-equilibrium materials such as amorphous, microcrystalline, quasicrystal, and nanocrystalline can be prepared via MIM, which has excellent electrical, magnetic, optical and mechanical properties.
3) It’s easy to carry out various types of recombination, giving full play to the respective characteristics of each component material, and is a process technology for producing high-performance metal-based and ceramic composite materials at low cost.
4) Near net formation and automated mass production can be achieved, thereby effectively reducing production resources and energy consumption.
2. What is the detailed manufacturing process?
After understanding the characteristics of MIM, we should focus on the specific manufacturing process.
2.1 Feedstock compounding
The Feedstock compounding process includes powder preparing, powder mixing, and other steps. The properties of metal powder have a major impact on the molding and sintering process as well as the quality of the product. Plasticizers such as engine oil, rubber or paraffin are usually added to improve the moldability and plasticity of the powder.
The injection molding process includes four steps of loading, pressing, holding and demolding. The pressing process means pressing the powder into the desired shape under a pressure of 15-600 MPa. You need to pay attention to the accuracy of the mold and the powder ratio.
It is carried out in a high-temperature furnace or a vacuum furnace which protects the atmosphere gas. Sintering differs from metal melting in that at least one element remains in the solid state in the sintering process.
During the sintering process, the powder particles become a metallurgical product with a certain porosity by a series of physical and chemical processes such as diffusion, recrystallization, fusion welding, compounding and dissolution.
2.4 Post-processing steps
In general, sintered parts can be used directly. However, some parts requiring high precision and wear resistance are subjected to post-sintering treatment.
Post-treatment includes coining, rolling, extrusion, quenching, surface hardening, oil immersion, and infiltration.
MIM has a series of advantages such as remarkable energy saving, material saving, excellent performance, high product precision and good stability, which is very suitable for mass production.
In addition, some materials and complex parts that cannot be prepared by conventional casting methods and mechanical processing methods can also be manufactured by MIM technology, and thus have received much attention from the industry.
That’s all about the manufacturing process of MIM, and we hope it’d be useful! Feel free to leave your comments below if you have any question.
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